Nipple size?

Makayla

My LO just turned 4 months and is still on size 1 slow flow nipple in her bottles. (EBF) - I guess I was under the impression that breast fed babies always stayed on size 1? But yesterday my mom asked me when I was going to get her the next size. She is pace fed when I’m at work so she shouldn’t be getting too much air or anything, isn’t gassy and doesn’t really bspit up.

Just curious what size nipple everyone is using?